Multicasting is a well-know method of transmitting information to selected groups of users across a network, such as the Internet. For example, the transmission of an e-mail message to a group of users, each user being listed on a mailing list, uses multicasting principles. Video conferencing and teleconferencing also use multicasting principles and, accordingly, are often referred to as “multi-conferencing.”
Due to the increased demand for uses utilizing multicasting principles, protocols such as the Internet Group Multicast Protocol (“IGMP”) have been developed and refined to support multicasting over a Transmission Control Protocol/Internet Protocol (“TCP/IP”) network, such as the Internet. The new protocols, such as IGMP, allow users to easily create and join multicasting session (“multicasts”). However, in some protocols, such as Multicast Extensions to Open Shortest Path First (“MOSPF”) protocol, changes in, for example, the number of users in a multicast, or the creation of a new multicast, cause a network running these protocols to recalculate “route information” across the network. In other words, the changes cause a network running these protocols to recalculate the information the network uses to forward a multicast from a source to a user. In general, route information recalculations increase overhead costs, such as memory allocation and processor utilization. Moreover, route information recalculations limit the physical size of a network running these protocols.